Buying a place in Sant Cugat are still totally overpriced compared to what you can find by renting. Remember that listed rents are "suggested" and you are expected to negotiate the price down.
Make sure you look at the neighbor's yard to see if they have dogs. There are some houses with really loud dogs that will drive you nuts.
Due to overly friendly tenant laws, you will be expected to make a deposit of several (2-6) months rent (there's also some kind of bank escrow thing you can do, but its usually more pain than its worth). The reason behind this is that it can take up to 6 months to kick out a non-paying tenant. If you work for a big company, getting a letter saying how important you are sometimes helps lower the amount. People here are unduly impressed by fancy business cards. Make sure you get some, even if you haven't really started your new job yet.
Something to remember: if you haven't made a deposit for the place, it's not yours! Most likely the agent is trying to shop it around to other people and get a better price. So if you find a better place in the meanwhile, don't feel guilty about blowing off a previous place.
There seems to be a pattern of people half-heartedly trying to rent out their place. If their furniture is still there, don't waste your time, they are not serious.
If you use an agent (or the owner uses one), it will cost you one months rent in fees, so you might be better off looking in Tot Sant Cugat (a little free red magazine that's always laying around somewhere).
If you think your rent is a rip-off, then just phone your landlord and say that you are moving unless they lower the rent. It helps if you can mention a similar place that is significantly cheaper. It's really that easy.